Add tool-requirements subcommand

app/ghcup-gen/GHCupInfo.hs

+module GHCupInfo where
+
+import           GHCupDownloads
+import           ToolRequirements
+import           GHCup.Types
+
+
+ghcupInfo :: GHCupInfo
+ghcupInfo = GHCupInfo { _toolRequirements = toolRequirements
+                      , _ghcupDownloads   = ghcupDownloads
+                      }

app/ghcup-gen/Main.hs

@@ -9,9 +9,10 @@
 
 module Main where
 
+import           GHCup.Types
 import           GHCup.Types.JSON               ( )
 import           GHCup.Utils.Logger
-import           GHCupDownloads
+import           GHCupInfo
 
 import           Data.Aeson                     ( eitherDecode )
 import           Data.Aeson.Encode.Pretty
@@ -135,7 +136,7 @@ main = do
           GenJSON gopts -> do
             let
               bs = encodePretty' (defConfig { confIndent = Spaces 2 })
-                                 ghcupDownloads
+                                 ghcupInfo
             case gopts of
               GenJSONOpts { output = Nothing }        -> L.hPutStr stdout bs
               GenJSONOpts { output = Just StdOutput } -> L.hPutStr stdout bs
@@ -159,7 +160,7 @@ main = do
 
  where
   valAndExit f contents = do
-    av <- case eitherDecode contents of
+    (GHCupInfo _ av) <- case eitherDecode contents of
       Right r -> pure r
       Left  e -> die (color Red $ show e)
     myLoggerT (LoggerConfig True (B.hPut stdout) (\_ -> pure ())) (f av)

app/ghcup-gen/ToolRequirements.hs

+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE QuasiQuotes       #-}
+
+module ToolRequirements where
+
+import           GHCup.Types
+import           GHCup.Utils.String.QQ
+
+import qualified Data.Map                      as M
+
+
+
+-- | Currently 'GHC' is used for both GHC and cabal to simplify
+-- this, until we need actual separation.
+toolRequirements :: ToolRequirements
+toolRequirements = M.fromList
+  [ ( GHC
+    , M.fromList
+      [ ( Nothing
+        , M.fromList
+          [ ( Linux UnknownLinux
+            , M.fromList
+              [ ( Nothing
+                , Requirements
+                  []
+                  [s|You need the following packages: curl g++ gcc gmp make ncurses realpath xz-utils. Consult your distro documentation on the exact names of those packages.|]
+                )
+              ]
+            )
+          , ( Linux Alpine
+            , M.fromList
+              [ ( Nothing
+                , Requirements
+                  [ "curl"
+                  , "gcc"
+                  , "g++"
+                  , "gmp-dev"
+                  , "ncurses-dev"
+                  , "libffi-dev"
+                  , "make"
+                  , "xz"
+                  , "tar"
+                  , "perl"
+                  ]
+                  ""
+                )
+              ]
+            )
+          , ( Linux Ubuntu
+            , M.fromList
+              [ ( Nothing
+                , Requirements
+                  [ "build-essential"
+                  , "curl"
+                  , "libgmp-dev"
+                  , "libffi-dev"
+                  , "libncurses-dev"
+                  , "libtinfo5"
+                  ]
+                  ""
+                )
+              ]
+            )
+          , ( Darwin
+            , M.fromList
+              [ ( Nothing
+                , Requirements
+                  []
+                  "On OS X, in the course of running ghcup you will be given a dialog box to install the command line tools. Accept and the requirements will be installed for you. You will then need to run the command again."
+                )
+              ]
+            )
+          , ( FreeBSD
+            , M.fromList
+              [ ( Nothing
+                , Requirements
+                  [ "curl"
+                  , "gcc"
+                  , "gmp"
+                  , "gmake"
+                  , "ncurses"
+                  , "perl5"
+                  , "libffi"
+                  , "libiconv"
+                  ]
+                  ""
+                )
+              ]
+            )
+          ]
+        )
+      ]
+    )
+  ]

app/ghcup/Main.hs

@@ -13,6 +13,8 @@ module Main where
 import           GHCup
 import           GHCup.Download
 import           GHCup.Errors
+import           GHCup.Platform
+import           GHCup.Requirements
 import           GHCup.Types
 import           GHCup.Utils
 import           GHCup.Utils.Logger
@@ -79,6 +81,7 @@ data Command
   | Compile CompileCommand
   | Upgrade UpgradeOpts
   | NumericVersion
+  | ToolRequirements
 
 data ToolVersion = ToolVersion Version
                  | ToolTag Tag
@@ -218,6 +221,11 @@ com =
                (   (\_ -> NumericVersion)
                <$> (info (helper) (progDesc "Show the numeric version"))
                )
+          <> command
+               "tool-requirements"
+               (   (\_ -> ToolRequirements)
+               <$> (info (helper) (progDesc "Show the requirements for ghc/cabal"))
+               )
           <> commandGroup "Other commands:"
           <> hidden
           )
@@ -615,7 +623,7 @@ main = do
                       , DownloadFailed
                       ]
 
-          dls <-
+          (GHCupInfo treq dls) <-
             ( runLogger
               . flip runReaderT settings
               . runE @'[JSONError , DownloadFailed]
@@ -779,6 +787,21 @@ Check the logs at ~/.ghcup/logs and the build directory #{tmpdir} for more clues
                         runLogger ($(logError) [i|#{e}|]) >> exitFailure
 
             NumericVersion -> T.hPutStr stdout (prettyPVP ghcUpVer)
+            ToolRequirements -> (runLogger $ runE
+                      @'[ NoCompatiblePlatform
+                        , DistroNotFound
+                        , NoToolRequirements
+                        ] $ do
+                platform <- liftE $ getPlatform
+                req <- (getCommonRequirements platform $ treq)
+                         ?? NoToolRequirements
+                liftIO $ T.hPutStr stdout (prettyRequirements req))
+              >>= \case
+                    VRight r -> pure r
+                    VLeft e ->
+                      runLogger
+                          ($(logError) [i|Error getting tool requirements: #{e}|])
+                        >> exitFailure
   pure ()
 
 

ghcup.cabal

@@ -283,6 +283,7 @@ library
     GHCup.Download.Utils
     GHCup.Errors
     GHCup.Platform
+    GHCup.Requirements
     GHCup.Types
     GHCup.Types.JSON
     GHCup.Types.Optics
@@ -368,8 +369,11 @@ executable ghcup-gen
 
   --
   main-is:          Main.hs
-  other-modules: GHCupDownloads
-                 Validate
+  other-modules:
+    GHCupDownloads
+    GHCupInfo
+    ToolRequirements
+    Validate
 
   -- other-extensions:
   build-depends:    ghcup

lib/GHCup/Download.hs

@@ -94,7 +94,7 @@ getDownloads :: ( FromJSONKey Tool
                 , MonadFail m
                 )
              => URLSource
-             -> Excepts '[JSONError , DownloadFailed] m GHCupDownloads
+             -> Excepts '[JSONError , DownloadFailed] m GHCupInfo
 getDownloads urlSource = do
   lift $ $(logDebug) [i|Receiving download info from: #{urlSource}|]
   case urlSource of

lib/GHCup/Errors.hs

@@ -92,6 +92,9 @@ data TooManyRedirs = TooManyRedirs
 data PatchFailed = PatchFailed
   deriving Show
 
+-- | The tool requirements could not be found.
+data NoToolRequirements = NoToolRequirements
+  deriving Show
 
 
     -------------------------

lib/GHCup/Requirements.hs

+{-# LANGUAGE OverloadedStrings #-}
+
+module GHCup.Requirements where
+
+import           GHCup.Types
+import           GHCup.Types.JSON               ( )
+import           GHCup.Types.Optics
+
+import           Control.Applicative
+import           Data.Maybe
+import           Optics
+import           Prelude                 hiding ( abs
+                                                , readFile
+                                                , writeFile
+                                                )
+
+import qualified Data.Text                     as T
+
+
+-- | Get the requirements. Right now this combines GHC and cabal
+-- and doesn't do fine-grained distinction. However, the 'ToolRequirements'
+-- type allows it.
+getCommonRequirements :: PlatformResult
+                      -> ToolRequirements
+                      -> Maybe Requirements
+getCommonRequirements pr tr =
+  preview (ix GHC % ix Nothing % ix (_platform pr) % ix (_distroVersion pr)) tr
+    <|> preview (ix GHC % ix Nothing % ix (_platform pr) % ix Nothing) tr
+    <|> preview
+          ( ix GHC
+          % ix Nothing
+          % ix (set _Linux UnknownLinux $ _platform pr)
+          % ix Nothing
+          )
+          tr
+
+
+prettyRequirements :: Requirements -> T.Text
+prettyRequirements Requirements {..} =
+  let d = if not . null $ _distroPKGs
+        then
+          "\n  Install the following distro packages: "
+            <> T.intercalate " " _distroPKGs
+        else ""
+      n = if not . T.null $ _notes then "\n  Note: " <> _notes else ""
+  in  "System requirements " <> d <> n

lib/GHCup/Types.hs

@@ -12,6 +12,39 @@ import qualified GHC.Generics                  as GHC
 
 
 
+    --------------------
+    --[ GHCInfo Tree ]--
+    --------------------
+
+
+data GHCupInfo = GHCupInfo
+  { _toolRequirements :: ToolRequirements
+  , _ghcupDownloads   :: GHCupDownloads
+  }
+  deriving (Show, GHC.Generic)
+
+
+
+    -------------------------
+    --[ Requirements Tree ]--
+    -------------------------
+
+
+type ToolRequirements = Map Tool ToolReqVersionSpec
+type ToolReqVersionSpec = Map (Maybe Version) PlatformReqSpec
+type PlatformReqSpec = Map Platform PlatformReqVersionSpec
+type PlatformReqVersionSpec = Map (Maybe Versioning) Requirements
+
+
+data Requirements = Requirements
+  { _distroPKGs :: [Text]
+  , _notes      :: Text
+  }
+  deriving (Show, GHC.Generic)
+
+
+
+
 
     ---------------------
     --[ Download Tree ]--
@@ -99,7 +132,7 @@ data DownloadInfo = DownloadInfo
 -- | Where to fetch GHCupDownloads from.
 data URLSource = GHCupURL
                | OwnSource URI
-               | OwnSpec GHCupDownloads
+               | OwnSpec GHCupInfo
                deriving Show
 
 

lib/GHCup/Types/JSON.hs

@@ -39,6 +39,8 @@ deriveJSON defaultOptions { fieldLabelModifier = removeLensFieldLabel } ''VUnit
 deriveJSON defaultOptions { fieldLabelModifier = removeLensFieldLabel } ''VersionInfo
 deriveJSON defaultOptions { fieldLabelModifier = removeLensFieldLabel } ''Tag
 deriveJSON defaultOptions { fieldLabelModifier = removeLensFieldLabel } ''DownloadInfo
+deriveJSON defaultOptions { fieldLabelModifier = removeLensFieldLabel } ''GHCupInfo
+deriveJSON defaultOptions { fieldLabelModifier = removeLensFieldLabel } ''Requirements
 
 
 instance ToJSON URI where
@@ -69,11 +71,11 @@ instance FromJSONKey Versioning where
 instance ToJSONKey (Maybe Versioning) where
   toJSONKey = toJSONKeyText $ \case
     Just x  -> prettyV x
-    Nothing -> T.pack "unknown_version"
+    Nothing -> T.pack "unknown_versioning"
 
 instance FromJSONKey (Maybe Versioning) where
   fromJSONKey = FromJSONKeyTextParser $ \t ->
-    if t == T.pack "unknown_version" then pure Nothing else pure $ just t
+    if t == T.pack "unknown_versioning" then pure Nothing else pure $ just t
    where
     just t = case versioning t of
       Right x -> pure x
@@ -112,6 +114,19 @@ instance ToJSONKey Architecture where
 instance FromJSONKey Architecture where
   fromJSONKey = genericFromJSONKey defaultJSONKeyOptions
 
+instance ToJSONKey (Maybe Version) where
+  toJSONKey = toJSONKeyText $ \case
+    Just x  -> prettyVer x
+    Nothing -> T.pack "unknown_version"
+
+instance FromJSONKey (Maybe Version) where
+  fromJSONKey = FromJSONKeyTextParser $ \t ->
+    if t == T.pack "unknown_version" then pure Nothing else pure $ just t
+   where
+    just t = case version t of
+      Right x -> pure x
+      Left  e -> fail $ "Failure in (Maybe Version) (FromJSONKey)" <> show e
+
 instance ToJSON Version where
   toJSON = toJSON . prettyVer
 

lib/GHCup/Types/Optics.hs

@@ -19,6 +19,7 @@ makeLenses ''DownloadInfo
 makeLenses ''Tag
 makeLenses ''VersionInfo
 
+makeLenses ''GHCupInfo
 
 uriSchemeL' :: Lens' (URIRef Absolute) Scheme
 uriSchemeL' = lensVL uriSchemeL